中国科学院云南天文台机构知识库

通过精确的偏振测量实现太阳中低层磁场遥感是1 m口径红外太阳望远镜的重要科学任务。为了实现高精度高效率的系统偏振定标,需要对望远镜系统进行偏振建模。分析了该望远镜折轴光路仪器偏振的周天和季节变化,以及望远镜真空封窗的应力双折射效应。结果显示折轴光路的偏振效应主要表现为线偏振与圆偏振之间的交扰,交扰程度最大达0.7。同时,由于像旋速度巨大,临近夏至期间太阳接近中天时偏振交扰会呈现一个震荡过程。封窗在重力和真空载荷的共同作用下,总的偏折特性可等效为一个位相延迟片;并且延迟量随望远镜高度角变化而变化。当望远镜指向水平时偏振交扰最明显,达1.2×10-2。

An important scientific task of new vacuum solar telescope (NVST) is to obtain the middle and lower magnetic field of solar by accurate polarization measurement. In order to achieve high precision and high efficiency systematic polarization calibration, it is needed to build a polarization model for the telescope. This article analyzes the telescope instrumental polarization changes of coude optical path over days and seasons, and birefringence effects of its vacuum window. The result shows: the main crosstalk of Coude optical path is between linear polarization and circuit polarization, whose maximum number is 0.7. In the meantime, when the sun approaches midheaven around the summer solstice, the curve of crosstalk becomes shocked since dramatic derotation. And the total polarization property of vacuum window is equivalent to a retarder which changes along with the altitude of telescope. It becomes obvious when the telescope points are horizontal and the crosstalk increases to 1.2 × 10~(-2).